The present invention relates to a seagoing high-speed ship having an electrical steering propeller which has a polyphase electric motor which is mounted under the stern of the ship via a shaft which can rotate and preferably has two parts in a gondola-like housing, and can be supplied with electrical drive power via a slipring arrangement which can be rotated via drive motors.
CA 1,311,637 A discloses an electrical steering propeller having a tubular shaft inside the ship with a slipring body located above the shaft. The prospectus from Siemens and Schottel, entitled xe2x80x9cThe SSP Propulsorxe2x80x9d, No. 159U559 04982, April 1998, also discloses a steering propeller which can be rotated, in which the sliprings for transmission of the electrical drive power are arranged the same way as the hydraulic drive motors for the rotary movement with their hydraulic pumps located in a drive machine room (Propulsor 500 m) above the steering propeller. Cables located from above are supplied to the sliprings.
The object of the present invention is to refine known drives such that more space is obtained in the stern of the ship. This is particularly important in Roro-ships where it is desirable to construct a continuous internal car deck without the stern door for the car deck, or the car deck itself, having to be raised. It is also important to retain adequate capabilities for repair and maintenance. It is a further object to design conditions downstream from the stern to minimize drag, taking into account the flow conditions resulting from the use of steering propellers.
These objects are achieved by mounting the steering propeller in the stern of the ship via a flat collar bearing in the vicinity of the outer skin, and preferably above the waterline. The slipring arrangement is accommodated in the upper part of the shaft at the level of the annular bearing, and with the drive motors for the rotary movement being physically small and arranged at least partially in the interior of the collar bearing in order to achieve a small installed arrangement for the electrical steering propeller. While at first blush it may appear to be impossible to accommodate the sliprings and the drive motors in the upper part of the shaft due to the construction of its xe2x80x9crotating bearingxe2x80x9d and still provide a downward passage, the invention is made feasible by optimizing the sizes of all the parts and by largely dispensing with horizontally running struts. This makes it possible to move the drive motors to the area under the slipring arrangement.
The flat collar bearing can be arranged both above the waterline and below the waterline. In the case of an arrangement below the waterline, it is advantageous to maintain an increased pressure. However, the arrangement disclosed in CA 1,311,657A, where the shaft enters the ship below the waterline with an internal extension of the shaft above the waterline, is considerably less advantageous since seawater can enter the interior of the bearing.
Where the shaft is mounted in a large-diameter collar bearing above the waterline, and the bearing diameter is approximately equal to or greater than the winding length of the electric motor, this results in the upper part of the shaft of the steering propeller being sufficiently spacious that the slipring arrangement and the rotating motors can be accommodated completely inside the shaft. This is especially true when the collar bearing also has a large internal diameter. Accordingly, it is possible to dispense with a separate machine room above the steering propeller with a concomitant saving in installed height. The collar bearing can be arranged directly under the car deck.
The present invention further provides for the drive motors to be in the form of flat hydraulic radial piston motors. This results in a particularly advantageous configuration of the rotating motors since they have small dimensions and a large torque.
The present invention advantageously provides for the possibility of connecting the shaft to the ship""s hull via an intermediate covering part immediately under the lowermost cargo deck in the stern, for example the car deck in the case of Roro-ships. Such an intermediate covering part, which may also be in the form of an annular disk, advantageously results in the ability to install the electrical steering propeller such that it is both stable and physically small. The intermediate covering part can be arranged in the stern area both via mounting elements such as boxes, and directly by fitting it on to a double bottom. It is particularly advantageous in the case of Roro-ships if the shaft is mounted under a steering propeller sealing cover in the ship""s stern, with the sealing cover being a component of the car deck. This results in particularly good utilization of the physical height available in the stern of the ship, which allows vehicles to be driven directly onto the inner car deck via the stern door. This allows the car deck to be used over the full length of the ship, thus resulting in significantly improved space utilization for the main car deck. Full utilization of the weather-deck area is likewise ensured, in which case the capstan drives etc. can advantageously be arranged under the weather deck in order to enlarge the usable area.
A preferred embodiment of the present invention is where the sealing cover is provided with access openings to individual components in the steering propeller, for example, to the slipring arrangement, to the drive motors, and to other essential functional elements. This eliminates the need to remove the sealing cover in the car deck while performing servicing work and minor repairs, since the components can be accessed via the openings.
Further, the present invention advantageously provides for the upper part of the steering propeller to be sealed in a fire-resistant manner from the lowermost deck in the stern area. This makes it possible to comply with the safety requirements for Roro or Ropax ships without needing to modify the advantageous configuration of the electrical steering propeller which only requires a minimal installed height.
The present invention furthermore provides the electrical steering propeller with sliprings for supplying power to and monitoring the motor which are at least partially in the form of concentric sliprings. This results in a small physical shape for power supply and signal transmission components. For electrical motors having more than three phases, for example 6-phase or 12-phase electric motors, as well as for split electric motors, the present invention provides for the power supply sliprings to be designed to have only three phases, and for a junction to a motor winding system having more than three phases to be made behind the slipring arrangement via power semiconductors, which form a local converter arranged in the shaft. It is thus also possible to supply power to polyphase or split electric motors with a physically small, relatively simply slipring body. This considerably simplifies the construction and considerably reduces the physical height of the slipring arrangement. Polyphase winding systems can thus be supplied with electrical power in a controlled, advantageous manner. The power semi-conductors can be cooled via heat dissipation elements which are connected to the shaft casing by the seawater flowing around it.
The cables for power transmission are advantageously routed from the side to the slipring arrangement of the shaft. While this requires a separate connecting element on the slipring arrangement, the additional costs incurred as a result of this are more than compensated for by the gain in space. The connecting element can advantageously run between the vehicle lanes on the car deck of a Roro-ship. This therefore does not detract from the small installed height of the steering propeller.
As a result of the arrangement of the drives for the rotary movement and for the slipring body in the shaft upper part, they are close to the auxiliary appliances in the shaft, for example the bilge pumps and oil pumps, etc. If required, power semiconductors are also located in this area, since the lower shaft part is designed to be narrow to assist the flow and also act as a rudder. Further, since it is impossible to prevent heat accumulations from being formed, at least one fan can be arranged in the upper part of the shaft, which allows air to circulate in the shaft upper part, and if necessary, also allows air to be interchanged.
In a further preferred embodiment of the present invention, the transition from the upper part to the lower part of the shaft may be located at the same level as the outer skin of the ship, preferably entirely above the waterline. The flange between the upper part and lower part of the shaft can thus be removed from the flow around the hull, thus allowing the shaft to be replaced with the electric motor for repairs without any need for the ship to be docked. For reliably xe2x80x9cdryxe2x80x9d replacement, it is sufficient for the ship to be trimmed bow-down.
In yet a further preferred embodiment of the invention, the motor shaft of the steering propeller is inclined at an angle matched approximately to the stern profile of the ship. This results in a downstream flow in the stern area of the ship which makes use of the flow accelerated by the propellers to reduce the stern drag of the ship. The steering propeller according to the present invention can thus be arranged right at the stern without causing any disadvantageous effects on the flow. This advantageous configuration results in the maximum amount of space being gained. Thus, overall, not only does the use of the steering propeller according to the invention, with a small installed height, result in better utilization of the space available in the stern area of the ship""s hull, but there is also no deterioration in the flow in the stern area in comparison to conventional steering propellers arranged more deeply under the ship.